Doors have customarily been secured by locks having a latch or bolt going from the door into a doorjamb or door frame or by a sliding bolt or door chain inside. Locks inside a door knob can be easily opened by placing a pipe wrench on the door knob until the lock breaks. Dead Bolt locks have the disadvantage as do all locks of being unlocked by anyone with a duplicate or master key.
In many cases a lock, bolt, door frame or door chain are so weak that a strong blow to the door will cause them to break and the door to open. A door can also be forced open by jimmying it or by pushing the latch back with a thin flexible material or cutting the bolt.
Added security can be obtained by placing a chair against the door by inserting the top of the back of the chair under the door knob and the two back legs of the chair on the floor. However, a chair is not designed for this purpose and it fits loosely and therefore can be dislodged from its position. Also, a chair is rigid and a great deal of force must be exerted in trying to make it fit tightly against the door. Placing a chair against a door is also a nuisance in that the chair extends out into the room and is a safety hazard not to mention the loss of use of the chair for its intended purpose.
Attempts to solve the above problems have been virtually fruitless. One known apparatus is a rigid device having a V-shape at the top where the V-shape end is placed under the door knob and the other end is placed on the floor. These type of apparatus still have the disadvantage of being rigid and it is virtually impossible to force them against the door so that they will fit tightly. One can kick them or hammer on them but the result is still a loose fit which makes it easy to dislodge and virtually useless as a security device.